Lake Storsjön's shores have long been inhabited. Though the area where Östersund is situated was for a very long time Frösön's link to the east mainland. Frösön, the island of the Norse god Freyr, was originally the centre of the region and it was here the only inland Scandinavian hill fort, Mjälleborgen, was built around 300 AD. The ancient Scandinavian thing Jamtamót was held on this island, the christening of Jämtland begun here and it was here the World's northern-most raised runestone, Frösö Runestone, was risen.
Plans regarding the foundation of a Swedish city or köping (market town, "Chipping") in Jämtland existed amongst governmental officials already after the previously Norwegian province was ceded from Denmark-Norway in 1645. Queen Christina demanded the establishment of a sconce on Andersön shortly after the province became Swedish, this sconce would together with Frösö sconce secure the Swedish control over Jämtland. Christina's intention was to locate the "Jamts' city" within this fortification. In order to construct the sconce the local inhabitants were coerced into forced labour 1651 but after protests and lack of capital the project was ended in 1654.
In 1758, the plans were brought back up through an initiative from the chief financial officerPehr Schissler and the proposition did however initiate a new debate whether or not a city was to be established in Jämtland, in order to counteract the trading and faring traditions of Jämtland's farmers. Several other attempts at constraition had previously been taken, and deemed unsatisfactory. Östersund was founded and given its charter by Monarch Gustav III of Sweden the 23 October in 1786, shortly after the outskirt of the Odensala farmers' lands were bought for the purpose. Several other places had been suggested, like Huså the then largest settlement in Jämtland along with Krokom, Sunne and Ede outside of Brunflo. Frösön was also a candidate but the lot fell on Östersund, as it was